1. Field of the Invention
This application claims priority under 35 U.S.C. Section 119 to Japanese Patent Application No. 2013-101246 filed on May 13, 2013 and Japanese Patent Application No. 2014-065457 filed on Mar. 27, 2014, which are herein incorporated by reference.
The present invention relates to a hard coat film, and a polarizing plate and an image display apparatus each including the film.
2. Description of the Related Art
Hitherto, each of optical members such as a polarizing plate, and a screen and/or touch panel of an image display apparatus has been provided with a hard coat film in some cases for preventing flawing or light reflection in such member. The hard coat film includes a transparent film and a hard coat layer formed on the transparent film. The hard coat layer is typically formed of a thin coating film obtained by forming a hard coat layer-forming material containing, for example, a thermosetting resin or an ionizing radiation-curable resin such as a UV-curable resin into a film.
A considerable difference in refractive index between a transparent film and a hard coat layer exists in a related-art hard coat film. Accordingly, the presence of slight unevenness on a surface of the hard coat layer involves a problem in that an interference fringe occurs. It should be noted that the interference fringe is a striped patterned external appearance resulting from reflection of light from a three-wavelength light source such as a fluorescent lamp that has impinged on, for example, the surface of the hard coat layer. Such interference fringe involves a problem in that the interference fringe is responsible for a reduction in visibility of the surface of the hard coat film.
In addition, interlayer filling is adopted for the surface of the hard coat film in some cases for improving its visibility. To that end, the hard coat film needs to be made compatible with the interlayer filling. Specifically, in order that a state where an interlayer filler is uniformly applied may be maintained for a long time period, application property of the hard coat film needs to be improved so that the interlayer filler may not be repelled by the surface of the hard coat layer.
A method involving performing surface modification treatment based on hydrophilization is available as a method of making the hard coat film compatible with the interlayer filling. However, the method involves the following problem. The number of steps in its production increases to reduce productivity and its scratch resistance reduces.
In this context, the following hard coat film has been proposed as a method of preventing occurrence of the interference fringe (see Japanese Patent Application Laid-open No. 2011-237789). In a region from a space between a transparent film and a hard coat layer to a thickness-wise middle part of the hard coat layer, a refractive index continuously changes in the thickness direction. However, an attempt to make the hard coat film compatible with the interlayer filling involves a problem in that its scratch resistance reduces and an external appearance failure such as white haze occurs.
As described above, a hard coat film in which occurrence of an interference fringe is prevented and which is capable of interlayer filling has been demanded.